This is a prospective "two-pronged" study conducted in a total of 90 infants, all recruited in the first week of life, and followed until 4 months of life (Arm One), or until one year of life (Arm Two). Endogenous cholesterol fractional synthesis rate (FSR) is measured using the rate of incorporation of labeled hydrogen (the stable isotope deuterium oxide) into red blood cell membrane cholesterol. The current study tests the possibility of an imprinting effect of lipid intake early in life on cholesterol synthesis later in life.